Medical respirators

ABSTRACT

A liquid injector for use in a medical respirator having a cylinder mounted for movement within a cavity. The cavity has a supply of liquid thereto and as the cylinder moves therethrough, it entraps a quantity of liquid within the cylinder at the point when it is sealed against a closure within the cavity. A member is mounted for movement within the cylinder so that when the cylinder is moved against the closure, the member will be forced to move so as to eject the liquid entrapped therein into the stream of gas.

. United States Patent Bushman 1451 Apr. 24, 1973 [541 MEDICAL RESPIRATORS 3,162,050 12/1964 MacDonald et a1 ..73/422 0c 3,176,516 4/1965 Guenther ....73/422 GC [75] Andrew Bushman Cambndgei 3,493,148 2/1970 Cosner et al.... ....222/361 x England 3,521,634 7/1970 Goodyear et a1... ..128/188 73 A P 1,174,673 3/1916 Bye 128/218 NV Sslgnee ye "m Cambridge England 2,375,929 5/1945 Lautenschlfigen. 128/218 S [22] Filed: Jan. 29, 1970 l,363,l28 12/1920 Kitaoka ..l28/218 NV [21] Appl' T 6846 Primary ExaminerRichard A. Gaudet Assistant Examiner- 0. F. Dunne 30 Foreign Application Priority Data Arwmey-Frank Trifari Jan. 30, 1969 Great Britain ..5,l08/69 57 ABSTRACT 52 us. 01 ..l28/l88, 222/362 A liquid injector for use a medical respirator having 51 lm; c1. ..A6lm 17/00 a Cylinder for m Within a The 58 1 Field of Search ..l28/l88, 185-187, cavity has a supply of quid harm and as the 128/196 197 218 G 218 NV 218 R 218 S cylinder moves therethrough, it entraps a quantity of 54:15 1337/99 5 1 l 6 liquid within the cylinder at the point when it is sealed di 5 against a closure within the cavity. A member is mounted for movement within the cylinder so that [56] References Cied when the cylinder is moved against the closure, the member will be forced to move so as to eject the UNITED STATES PATENTS liquid entrapped therein into the stream of gas. 3,362,228 H1968 Stiiben ..73/422 GC 10 Claims, 4 Drawing Figures ear 62 71 PATENTEDAPR24 I975 INVENTOR.

' JOHN ANDREW BUSHMAN PATENTEDAPR 4 I975 SHEET 3 OF 3 Y Fig.4

, INVEN OR;

JOHN "ANDREW BUSHM'AN BY v AGENT MEDICAL RESPIRATORS The present invention relates to medical respirators.

In a medical respirator such as is used to assist breathing in cases of respiratory insufficiency and in anaesthesia it is a frequent requirement that a small amount of liquid, e.g., halothane or fluorothane, be added to the gas or mixture of gases being passed to the patient.

In such cases the amount of liquid passed to the patient during each inspiration is very small and requires to be precisely controlled. The mixing of gas and liquid must also be precisely controlled so that the gas is saturated to a required degree.

An object of the presentinvention is the provision of a liquid injector for a medical respirator in which the amount of liquid per inspiration delivered to a patient is adjustable. There is also provided a medical ventilator in which such liquid is mixed with the gas to the patient in such a way that a required degree of saturation of the gas is achieved.

According to one aspect of the present invention there is provided a liquid injector for a medical respirator for injecting a predetermined quantity of liquid into a stream of gas which is passed to a patient by the respirator, in which a volume of the liquid is enclosed in a container formed at least in part by two movable members movement of both of which, in unison or in sequence, causes the predetermined quantity of liquid to be transferred from the container into the stream of gas, the two members being adjustable in relation to each other to determine the said quantity.

The various features and advantages of the present invention will be apparent from the following description of exemplary embodiments thereof, taken in conjunction with the accompanying drawings in which:

FIG. 1 shows a diagram of a known type of liquid injector,

FIG. 2 shows a diagram of a liquid injector according to the invention, together with parts ofa respirator,

FIG. 3 shows another liquid injector according to the invention in which the sealing difficulties of FIG. 2 are avoided, and,

FIG. 4 shows a unitized construction of the injector and driving means of FIG. 3.

In the known type of fluid injector as shown in FIG. 1, a cylinder 30 having one open end has a side wall 31 and a closing end wall 32, the side wall 31 having two pairs of opposed ports 33, 34 and 35, 36 forming passages between outer and inner surfaces of the side wall. Slidable within the cylinder is a piston 37, sealed by normal means not shown to close any path between the inner face of side wall 31 and the outer cylindrical face of piston 37. The piston 37 is constructed with a portion of its length 38 of reduced diameter to provide within the cylinder 1 a volume 39 which may be moved along the axis of the cylinder by movement of the piston 37 whose end projects beyond the open end of cylinder 30 at all times.

In the position shown, a liquid flowing between ports 33 and 34 will fill volume 39 and subsequent movement of piston 37 to a position in which the reduced portion 38 lies between but is not exposed to ports 34 and 36 will carry a fixed amount of liquid out of the stream. Further movement of piston 37 to a position in which portion 38 is opposite ports 35 and 36 will enable the fixed volume of liquid to be removed via these ports,

e.g., by the passage of gas therethrough. As shown, gas will be trapped during the latter portion of movement of piston 37 between the inner end face of piston 37 and the end wall 32 and means such as a relief valve in the end wall may be used to prevent the trapped gas being compressed.

In the above construction the volume of liquid moved from one port to another is a constant quantity fixed by the diameter of the piston 37 and the length and diameter of the portion 38.

In accordance with one aspect of the invention, the volume is made variable between pre-set limits -by variation of the effective length of the portion 38. This could be achieved by constructing the piston 37 in two parts, 37A and 37B, the latter of which carries a threaded rod projecting through and engaging with an internal thread of an axial hole in part 37A. Rotation of the threaded rod external to the end of part 37A would then vary the length of a part corresponding to portion 38 and so vary the volume between the two ports A somewhat similar form of construction in accordance with the invention is shown in FIG. 2 in which a cylinder 40, open at both ends, has its wall 41 pierced by diametrically opposed ports 42, 43 and 44, 45. A piston 46 slides within the cylinder 40 and has two diametrical holes 47 and 48 situated so that they may simultaneously and respectively connect port 44 to port 45 and port 42 to port 43. The cylinder and piston may have co-operating means to prevent misalignment of holes and ports, or as shown, the external end of the piston may carry an arm 49, to which force to move the piston, such as provided by a pneumatic cylinder and piston, may be applied. Arm 49 may be arranged to engage with guides, not shown, to ensure alignment of holes and ports. The portion 46A of the piston projecting beyond the end of cylinder 40 has an axial hole 50 establishing communication between the diametrical hole 48 and the end of piston 46. Hole 50 is internally threaded and engaged therewith is an adjusting member 51, carrying an external thread engaged with the before-mentioned internal thread, of greater length than portion 46A of the piston. Rotation of member 51 will cause its end to project to a greater or lesser extent within the hole 48. It may be provided with an attached knob to facilitate adjustment and locked in position by lock nut, not shown, engaging the end face of piston 46. Preferably prevention of unwanted rotation is by other means, e.g., nylon as used in some types of shakeproof nut, which may also act as a seal, which must otherwise be separately provided, between member 51 and the internally threaded hole of piston portion 46A.

In the Figure a flow of liquid is arranged to occur through pipes 42A and 43A connected respectively to ports 42 and 43, and a pipe 19, connected to a cylinder F V of fixed volume, has its path completed, in the position shown, via port 44', diametrical hole 47 and port 45.

As stated earlier rotation of member 51 varies the amount of which the member projects within hole 48,

the dimensions of pistons 46, hole 48 and member 51 being such that, with member 51 fully entered in hole 48, the minimum required volume of liquid may be transferred by movement of piston 46 and, with the end of member 51 withdrawn to a position flush with the wall of hole 48, maximum desired volume is available.

During an expiration period of a respirator cylinder FV receives gas at pressure through pipe 19, and during such period hole 48 is arranged to connect ports 44 and 45. A predetermined small volume of liquid is thus swept into the cylinder FV. During an inspiration period, the injector is arranged to be in the position shown, hole 48 recharging with liquid and hole 47 allowing discharge of the gas and liquid in cylinder FV to a patient via pipe 19, the degree of saturation of the gas by the liquid being a function of the pressure of gas in cylinder FV and the volume of liquid previously passed thereto.

Movement of the piston 46 from the expiratory to the inspiratory position will transfer a small volume of gas to the liquid. Port 42 is therefore positioned above port 43 to allow such transferred gas to escape upwards through pipe 42A. Preferably also the direction of liquid flow is in the same direction, i.e., from port 43 to port 42, means such as a liquid reservoir having a vented air or gas space being provided to allow such transferred gas to escape from the liquid. It is also preferred that cylinder FV should be above port 44, any liquid within the cylinder FV then tending to drain out through pipe 19 and minimize collection of liquid within the cylinder.

In the arrangement of FIG. 2, sealing between piston 46 and the wall 41 of cylinder 40 must withstand the maximum pressure experienced by cylinder FV. Some mitigation of this difficulty may be achieved by inserting the injector of FIG. 2 in a lower pressure part of the system. This is readily achieved since such systems incorporate a flow restriction device for controlling the rate of gas flow from the supply (cylinder FV in the case of FIG. 2) to the patient. The liquid injection system can thus be inserted beyond this restriction. Under these conditions the piston 46 may be shortened by removal of that portion to the left of the dotted line 46B, diametrical hole 47 thus being removed from piston 46, movement of the hole 48 into alignment with ports 44 and 45 then being arranged to occur during an inspiratory period when gas is discharging .-from cylinder FV to the patient.

In either form of construction of the embodiment shown in FIG. 2, there is, due to member 51 projecting within hole 48, a possibility of gas, from a previous position of piston 46, remaining in hole 48 when in the shown position accepting liquid via ports 42 and 43, so reducing the volume of liquid transferred to ports 44 and 45 on the next stroke. To minimize this possibility, and also reduce entrainment of bubbles due to, for example, cavitation effects, FIG. 3 shows a preferred form of construction in which the sealing means do not traverse a port.

The construction provides an injector which comprises a cylinder which is moved by a first means against sealing means to entrap a volume ofa surrounding liquid, subsequent to which a piston, contained within the cylinder, is moved by a second means to eject the entrapped volume of liquid or a part thereof, the amount of the said ejected liquid being adjustable by alteration of the travel of the piston.

In FIG. 3, which is not to scale, a cavity 60 has a surrounding wall 61 and end walls 62 and 63. Ports 64 and 65 in wall 61 provide means whereby a liquid or liquid flow may be established within cavity 60. An open end of a cylinder 66 passes through wall 63, sealing means such as 0 rings 67 being provided to prevent egress of liquid around the cylinder. Within cavity 60 a valve seat 68 is attached to wall 62 and has an annular recess 69, which may carry a sealing ring 70 of resilient material, arranged to cooperate with the said open end of cylinder 66 when the latter is moved into engagement with seat 68. A passage through seat 68 and wall 62 is closed by a spring loaded non-return disc valve 71 external to wall 62, the spring loading being light, only preventing escape of liquid from cavity 60 under the conditions shown. Valve 71 is inserted as shown in a pipe line 20 carrying a gas, preferably at substantially atmospheric pressure during the period of liquid injection, into which the controlled amount of liquid is to be injected.

Within the bore of cylinder 66 lies a piston 72, which carries a plurality of sealing means such as piston or 0 rings 73, and has a piston rod 74 projecting through a partially closed end of cylinder 66 external of the wall 63. Coupled thereto, by means not shown, is the piston rod 75 of a pneumatic actuating cylinder 76, having an entry port 77 through which air may flow to move a piston 78 and a compression spring 79 which holds the piston 78 in the position shown in the absence of air pressure at port 77.

The wall at the open end of cylinder 76 carries, for a portion of its length, an internal thread 76A co-operating with an external thread on a portion 80A of an adjusting member 80, which has an annular projection 808 within the bore of the actuating cylinder 76. Rotation of member 80 or cylinder 76 relative to one another will therefore alter the position of projection 80B within the cylinder 76, so providing a variable limit to the travel of piston 78 and consequently, to piston 72.

Cylinder 66 has a flange 66A pierced by holes 668 slidable within which lie two arms 81 and 82 of a U- shaped drive member 83, having a driving rod 84 attached. Means such as nuts 85 and 86 engage with arms 81 and 82 preventing withdrawal of the arms 81 and 82 from flange 66A. Springs 87, under compression, surround the arms 81 and 82 and co-operate with the flange 66A and the base 83A of drive member 83. Driving rod 84 is operated by a pneumatic actuating cylinder, not shown, similar to cylinder 76.

In operation, rod 84 is first moved by its associated cylinder, this movement being transferred by springs 87 to cylinder 66 which engages valve seat 68 to enclose a volume of liquid within the space bounded by seat 68, cylinder 66 and piston 72. Little disturbance of the liquid occurs during this operation due to the relatively small size of the stroke and cylinder walls. Any further movement of rod 84 merely further compresses springs 87. Subsequent application of compressed air to actuating cylinder 76 will then move piston 78 and, hence, piston 72 and cause the latter to eject a volume of liquid into valve 71 and line 20, such volume depending on the position of adjusting member 80. Relief of air pressure within the actuating cylinders will then revert both cylinder 66 and piston 72 to the position shown.

The speed of operation of cylinder 66 and piston 72 in both directions may be controlled by needle valves in the supply and venting lines of the actuating cylinders.

Such a valve in the supply to port 77 may thus control the period of time in which liquid is being passed into gas flowing in pipe line 20, while the valves in the venting lines will control the relative positions of cylinder 66 and piston 72 during the return stroke.

As adjusting member 80 is not a moving part of the injector or driving mechanism, adjustment of the volume delivered may be readily made during operation of the injector.

Unit construction of the injector and pneumatic driving means of FIG. 3 is possible. Such unit construction is illustrated in FIG. 4 in which component parts having a similar function to those of FIG. 3 have the same references in both Figures. In FIG. 4 a cavity 60 is enclosed by side walls 61, end wall 62 and flange 88 of a member 89, and has ports 64 and 65 whereby a liquid or liquid flow may be established in the cavity. Within a bore 90 of member 89 lies a cylinder 66 having a flange 91, which may abut a portion 92 of member 89 which projects within the cavity, which co-operates with a spring 93, indicated by a series of circles, in contact with wall 62 and driving cylinder 66 towards the position shown. As in FIG. 3, valve seat 68, recess 69 resilient ring 70 and disc valve 71 allow liquid to be transferred to the gas line 20. Sealing means 67, indicated by part circles, prevent egress of liquid around the cylinder 66. Piston 72, sealed by piston rings 73, operates within the bore of cylinder 66 under the influence of piston rod 74. Piston rod 74 passes through the end wall 94 of cylinder 66 and a passage in the body of member 89, respective sealing means 95 and 96 such as O-rings preventing the escape air in bore 90; sealing means 67 also serving this purpose. A port 97 in member 89 communicates with bore 90 so that air at pressure applied to port 97 may drive cylinder 66 into engagement with seat 68 to enclose a volume ofliquid.

Rotatably engaged in a second bore 98 of member 89 is a boss 99 of an adjusting member 80. To secure the two members together boss 99 has a circumferential groove 100 in which may engage the end of a pin or screw (not shown) inserted in a hole 101 provided in member 89. As in FIG. 3, member 80 has a threaded portion 80A and an annular projection 808, the portion 80A mating with the internally threaded portion 76A of a pneumatic cylinder 76 which has an entry port 77, piston 78, piston rod 75 and a compression spring 79 indicated by a series of circles.

In FIG. 4 piston rods 74 and 75 comprise a single rod rigidity linking piston 73 and 78, the latter being provided with sealing means 102 such as O or piston rings, while in order that simultaneous application of air at the same pressure to ports 97 and 77 may operate cylinder 66 before the pistons, piston 78 may be of smaller diameter than cylinder 66 and/or spring 93 may be weaker than spring 79. In the embodiment shown, member 80 and cylinder 76 carry respective flanges 80C and 76B, the edges of which may be knurled to provide finger grip, whereby each may be rotated to provide the required adjustment. A first sleeve, indicated by broken lines 103 is attached to flange 80C and carries a circumferential percentage saturation scale. A helical slot and a second sleeve, of smaller diameter than the first, indicated by broken lines 104, is attached to flange 76B and carries a number of Tidal Volume" scales, portions of which are visible through the helical slot. A panel, through apertures in which the scales may be seen by the operator, is indicated by broken lines 105.

In both FIGS. 3 and 4 it is a requirement that cylinder 76 may be rotated. The pipe supplying air to port 77 is therefore of flexible construction and is coiled into a multi-turn helix to allow such rotation. Means, not shown, are also provided to prevent disengagement of threads A and 76A after initial assembly.

A medical respirator incorporating a fluid injector of the type shown in FIG. 3 or FIG. 4 may of course, also incorporate a fixed volume FV as shown in FIG. 2.

It will be apparent from the foregoing that a liquid injector in accordance with the invention may be used in association with any known medical respirator since all respirators have a patient gas stream into which the injector may be arranged to inject the required liquid. Also more than one injector may be used, if required, to provide injection for more than one liquid.

What we claim is:

l. A liquid injector, for injecting an adjustably predetermined quantity ofliquid into a stream of gas in a medical respirator, comprising a housing, a liquid supply chamber within the housing, means for supplying liquid to be injected to said chamber, a first member having a bore therein and arranged for movement with respect to the housing and into said chamber, an adjustably predetermined quantity of liquid in said chamber being entrapped within the bore of said first member for expulsion to the stream of gas when said member is moved into said supply chamber, a second member movable within the first member to provide an adjustable space within the bore and to cause liquid entrapped in the space to be injected to the stream of gas, and a non-return valve connected to said chamber through which the liquid from said space is injected into the gas stream, said members being arranged to occupy a position in the housing in which the space is connected to the liquid supply chamber so as to be filled with liquid therefrom when the first member is moved into the chamber, said members interrupting the means for supplying liquid to the chamber and connecting said space to the non-return valve for injection to the gas stream by movement of said second member within said first member.

2. The liquid injector according to claim 1 further comprising means for adjusting said second member with respect to the first member so that said space and the quantity of liquid entrapped therein is determined by adjustment of the second member.

3. The liquid injector according to claim 1 wherein said first and second members are arranged to be movable in unison.

4. The liquid injector according to claim 1 wherein said first movable member is a cylinder having one end thereof opened and the other end closed by said second member which is slidably mounted therein, and further comprising a closure means arranged so as to close the open end of said cylinder and form a container when said cylinder is moved towards said closure means and engaged therewith, said container comprising the closure means and said first and second members, said non-return valve being arranged on said closure means, said second member being arranged for movement toward the closure means so as to reduce the volume within said container and so as to expel the quantity of liquid contained within said container through said non-return valve and into the gas stream.

5. The liquid injector according to claim 4 further comprising means for causing adjustment of said second member so that the position from which said second member starts the said movement toward the closure is adjustable so as to vary the quantity of liquid within said first member.

6. The liquid injector according to claim 4 further comprising means for adjusting the position at which movement of said second member is stopped.

7. The liquid injector according to claim 4 further comprising pneumatic means for operating and causing movement of said first and second members.

8. A liquid injector for injecting a quantity of liquid into a stream of gas in a medical respirator comprising a housing, a cavity within said housing through which liquid to be injected to said gas is supplied, an open ended cylinder mounted for movement through said cavity, so that liquid is provided within said cylinder as it passes through said cavity, a piston movably mounted within said cylinder so as to provide means for adjusting the space within said cylinder and for causing the liquid within said cylinder to be ejected therefrom, closure means provided within said cavity so that when said cylinder is moved into contact with said closure means a container is formed, said liquid within said cylinder being contained therein, means connected to said cylinder for causing movement thereof through said cavity, a non-return valve connected to said closure means so as to provide a path of communication between said container and the stream of gas, and means connected to said piston for causing movement thereof within the cylinder so as to eject the liquid within the container into the stream of gas.

9. The liquid injector according to claim 8 wherein said cylinder and said piston are arranged so as to be movable in unison.

10. The liquid injector according to claim 8 further comprising means for adjusting the relative position of said piston within said cylinder so that the amount of liquid to be contained therein is controllable. 

1. A liquid injector, for injecting an adjustably predetermined quantity of liquid into a stream of gas in a medical respirator, comprising a housing, a liquid supply chamber within the housing, means for supplying liquid to be injected to said chamber, a first member having a bore therein and arranged for movement with respect to the housing and into said chamber, an adjustably predetermined quantity of liquid in said chamber being entrapped within the bore of said first member for expulsion to the stream of gas when said member is moved into said supply chamber, a second member movable within the first member to provide an adjustable space within the bore and to cause liquid entrapped in the space to be injected to the stream of gas, and a non-return valve connected to said chamber through which the liquid from said space is injected into the gas stream, said members being arranged to occupy a position in the housing in which the space is connected to the liquid supply chamber so as to be filled with liquid therefrom when the first member is moved into the chamber, said members interrupting the means for supplying liquid to the chamber and connecting said space to the non-return valve for injection to the gas stream by movement of said second member within said first member.
 2. The liquid injector according to claim 1 further comprising means for adjusting said second member with respect to the first member so that said space and the quantity of liquid entrapped therein is determined by adjustment of the second member.
 3. The liquid injector according to claim 1 wherein said first and second members are arranged to be movable in unison.
 4. The liquid injector according to claim 1 wherein said first movable member is a cylinder having one end thereof opened and the other end closed by said second member which is slidably mounted therein, and further comprising a closure means arranged so as to close the open end of said cylinder and form a container when said cylinder is moved towards said closure means and engaged therewith, said container comprising the closure means and said first and second members, said non-return valve being arranged on said closure means, said second member being arranged for movement toward the closure means so as to reduce the volume within said container and so as to expel the quantity of liquid contained within said container through said non-return valve and into the gas stream.
 5. The liquid injector according to claim 4 further comprising means for causing adjustment of said second member so that the position from which said second member starts the said movement toward the closure is adjustable so as to vary the quantity of liquid within said first member.
 6. The liquid injector according to claim 4 further comprising means for adjusting the position at which movement of said second member is stopped.
 7. The liquid injector according to claim 4 further comprising pneumatic means for operating and causing movement of said first and second members.
 8. A liquid injector for injecting a quantity of liquid into a stream of gas in a medical respirator comprising a housing, a cavity within said housing through which liquid to be injected to said gas is supplied, an open ended cylinder mounted for movement through said cavity, so that liquid is provided within said cylinder as it passes through said cavity, a piston movably mounted within said cylinder so as to provide means for adjusting the space within said cylinder and for causing the liquid within said cylinder to be ejected therefrom, closure means provided within said cavity so that when said cylinder is moved into contact with said closure means a container is formed, said liquid within said cylinder being contained therein, means connected to said cylinder for causing movement thereof through said cavity, a non-return valve connected to said closure means so as to provide a path of communication between said container and the stream of gas, and means connected to said piston for causing movement thereof within the cylinder so as to eject the liquid within the container into the stream of gas.
 9. The liquid injector according to claim 8 wherein said cylinder and said piston are arranged so as to be movable in unison.
 10. The liquid injector according to claim 8 further comprising means for adjusting the relative position of said piston within said cylinder so that the amount of liquid to be contained therein is controllable. 